1. Field of the Invention
The present invention relates to a probe plate used for a test of a semiconductor device, and it relates especially to a probe plate used for testing, wafer by wafer, the characteristic of a semiconductor device formed on a semiconductor wafer. The present invention also relates to a semiconductor test apparatus and a semiconductor test method using the probe plate as mentioned in the above.
2. Description of the Background Art
In general, in the process of manufacturing a semiconductor integrated circuit device (IC), the electric characteristics of a semiconductor device formed on a semiconductor wafer are measured with a test apparatus called a wafer prober for an IC test.
FIGS. 10A to 10C are perspective views showing known wafer prober as background art of the present invention in a disassembled state for clarity: FIG. 10A shows a test head, FIG. 10B shows a probe card and FIG. 10C shows part of a wafer; FIG. 11 is a perspective view showing the external appearance of a probe card seen from the bottom; FIG. 12 is a partly enlarged perspective view showing a state where a thin conductor needle (hereinafter referred to as a probe needle) is in touch with an electrode pad on a wafer; FIG. 13 is a cross-sectional view showing a state where a wafer prober is being used. In the following, the constitution of a wafer prober will be described referring to FIG. 10A to FIG. 13.
Referring to FIGS. 10A to 10C, a wafer 3 is marked off into a plurality of semiconductor chips 33 with scribe lines 32 provided on the wafer main surface 31. On each of these semiconductor chips 33 a semiconductor device such as an LSI (large scale integration) is made, and surrounding the semiconductor device many electrode pads 34 are provided for power supply and for input/output of signals.
In the examples shown in FIGS. 10A to 10C, to be able to test two pieces of chips as a unit, a plurality of thin probe needles 21 are provided on the probe card 2 so that they can face individual electrode pads on two pieces of semiconductor chips. The probe needles 21 are made of tungsten, chromium or an alloy of tungsten and chromium, and they are fixed on a surface of the probe card 2, made of an insulating material, with ring members 22 made of resin as shown in FIG. 11. The probe needles 21 are connected electrically with solder 24, etc., to a metallic pattern wiring 23 on the surface of the probe card 2.
The contact area of a probe needle 21 with the surface of an electrode pad 34 is about 50 to 100 .mu.m.phi.. An external diameter of a probe needle 21 on the side to be connected to a probe card 2 is about 200 to 300 .mu.m.phi.. The metallic pattern wiring 23 formed on the probe card 2 is electrically connected through through holes 25 to a metallic pattern wiring 26 formed on the surface opposite to the surface on which probe needles are connected. The metallic pattern wiring 26 is electrically connected to a metallic film part 27 having comparatively large area provided on the opposite side surface.
In the FIG. 10B are shown through holes, metallic pattern wiring 26 and metallic film parts 27 respectively, but actually each set of these parts is provided for each of the probe needles. There is provided an opening part 28 on the probe card 2 to visually confirm if probe needles 21 are making contact with electrode pads 34.
A test head 1 is a head of a test apparatus (hereinafter referred to as an IC tester) for judging the quality of an LSI by a functional operation test checking whether a logic circuit comprising an LSI, etc., operates properly, or by a DC test checking whether the logic circuit maintain a normal output voltage when it is loaded with a specified load. Pogo-pins 12 are provided to face metal film parts 27 on the probe card 2 around the opening part 11 on the test head 1. In FIG. 10A, several pogo-pins are shown for simplification. A pogo-pin gives a test signal to an LSI and receives a signal from the LSI.
Referring to FIG. 13, a wafer 3 is placed and fixed on a wafer chuck 4; the chuck 4 is held movably with a moving mechanism 5 in three directions which make a right angle with each other; the probe card 2 is fixed on a fixing part 6 of a wafer prober. A pogo-pin 12 of the test head 1 is pressed and abutted against a metal film part 27 on the probe card 2.
The procedure of a test of electric characteristics of a semiconductor device in the state of a wafer by using a wafer prober as mentioned in the above will be described in the following.
The electrode pads 34 on any two semiconductor chips 33 and the probe needles 21 fixed on the probe card 2 are aligned to be opposed and abutted with each other by using the moving mechanism 5. The probe needles 21 are made to make contact with the surfaces of electrode pads 34 by the movement of the wafer chuck 4 in the direction of an arrow mark A shown in FIG. 13.
The waveform of a signal to be given to an LSI is formed in the test head 1 and output from a pogo-pin 12. Because a pogo-pin is pressed and abutted against a metallic film part 27 on the probe card 2, the signal from the test head 1 is transmitted to the probe needles 21 soldered to a pattern wiring 23 through the metallic pattern wiring 26 extended from the metallic film part 27, a through hole 25 and the metallic pattern wiring 23, and the signal is applied to the LSI in the semiconductor chip 33 from the electrode pad 34. An output signal from the LSI is given to the test head 1 through the route in the reverse direction to the above, and it is given to an IC tester (not shown in the drawing) from the test head 1. The test of electric characteristics of an LSI is executed as described in the above.
As mentioned in the above, a wafer prober with which the electric characteristics of a plurality of semiconductor chips can be measured simultaneously has been known. The number of semiconductor chips which can be measured simultaneously is, however, limited by the following factors: an opening part 28 is needed for the visual confirmation of the contact between a probe needle 21 and an electrode pad 34, so that the probe needles 21 have to be disposed around the opening part 28; the outer diameter of a probe needles 21 on the side to be connected to the probe card 2 is large; and a certain area is needed to solder the probe needles 21 to the pattern wiring 23. Therefore, the number of semiconductor chips which can be measured simultaneously is limited to 2 or 3 pieces.
A test method for a semiconductor integrated circuit with which all the chips on a wafer can be measured without moving the wafer is disclosed in Japanese Patent Laid-Open No. 59-171131. In this application, the description as shown in the following is given: a base plate provided with a plurality of probe needles which is movable upward and downward selectively in a matrix form is placed over a semiconductor wafer on which a plurality of semiconductor integrated circuits are formed, and the desired probe needles are selectively moved upward and downward with a control system to touch the pads of semiconductor integrated circuits for measuring electric characteristics of the semiconductor integrated circuits.
In this test method, probe needles are depressed down with an air driving force, and when the air driving force is removed they are returned with spring forces. Therefore, when a desired needles is selected, it is necessary to depress down the desired needle with the air driving force and make the other needles return with the spring forces. In this test method, a probe needle is mechanically moved by an air driving force, so that it is a problem that a selecting action is slow.
A mechanism for moving a needle upward and downward has to be provided in the neighborhood of the needle, which limits the miniaturization of a device, and so it is difficult to apply this method to a device having small sized or small pitched pads.
When the size of an electrode pad is miniaturized to the order of 100 .mu.m.times.50 .mu.m and the pitch becomes less than 80 .mu.m, it becomes impossible to make a needle touch an electrode pad. When the size or pitch of an electrode pad to be made on a wafer is, the miniaturization the outer diameter of a probe needle must be miniaturized. When the outer diameter of a probe needles is miniaturized, however, the strength of the needle is weakened and also its manufacture becomes difficult, and further there is a problem that the mounting of the needle onto the probe card becomes difficult.
To solve the increasing difficulties in the manufacturing process in proportion to the miniaturization of a chip, a probe card in which a bump-shaped conductive prober is used in place of a probe needle is described in a Japanese Utility Model Laid Open No. 61-179747. FIG. 14 shows a cross-sectional view of such a conductive prober. Referring to FIG. 14, on a flexible insulating substrate 41 a through hole 42 is formed, and to the through hole 42 the plating 43 is given. On the plating 43 surrounding the through hole 42 a bump-shaped conductive prober is formed by dropping solder.
When the above-mentioned conductive prober is used, assembling work is facilitated comparing to the case of a probe needle 21. The bump-shaped conductive prober is, however, formed by dropping solder hence it is difficult to form the prober with high precision.